Biology subjects

Licheva, M.

Publications and source records attributed to Licheva, M..

2 recordsLinked to original sources

bioRxiv2026

In situ visualization of autophagy suggests vesicle fusion can contribute to phagophore expansion

The autophagy core machinery mediates the enclosure of cytosolic cargo destined for degradation in the lysosome. The Atg9-Atg2-Atg18 complex coordinates phagophore expansion via directed lipid transfer until closure of the phagophore rim. Using an Atg2 variant (Atg2-PM4) as a model of decelerated autophagosome biogenesis, we visualized the morphological states prior to autophagosome closure by cryogenic correlative light and electron microscopy in S. cerevisiae. Using in situ cryo-electron tomography, we find an enlarged rim morphology of an expanding phagophore in Atg2-PM4 cells in comparison with Atg2 wildtype condition. Analysis of segmented rim membrane features as well as surrounding and attached vesicles suggest that the enlarged rims are a result of cytosolic vesicles fusing with the growing phagophore. High-resolution imaging in this study shows that, apart from the initial nucleation phase, vesicle fusion can also contribute to phagophore expansion during later stages of autophagosome biogenesis.

cell biology↗

bioRxiv2022

mRNA targeting eliminates the need for the signal recognition particle during membrane protein insertion in bacteria

Signal-sequence dependent protein targeting is essential for the spatiotemporal organization of eukaryotic and prokaryotic cells and facilitated by dedicated protein targeting factors, such as the signal recognition particle (SRP). However, targeting signals are not exclusively contained within proteins, but can also be present within mRNAs. By in vivo and in vitro assays, we show that mRNA targeting is controlled by the nucleotide content and by secondary structures within mRNAs. mRNA binding to bacterial membranes occurs independently of soluble targeting factors, but is dependent on the SecYEG-translocon and YidC. Importantly, membrane insertion of proteins translated from membrane-bound mRNAs occurs independently of the SRP pathway, while the latter is strictly required for proteins translated from cytosolic mRNAs. In summary, our data indicate that mRNA targeting acts in parallel to the canonical SRP-dependent protein targeting and serves as an alternative strategy for safeguarding membrane protein insertion when the SRP pathway is compromised.

microbiology↗